Critical role of C/SiO2 composite coating in enhancing the mechanical and antioxidation properties of 3D needled carbon fibers

Herein, a hydrothermal carbonization coating/SiO2 (HTCC/SiO2) composite coating on 3D needled carbon fibers (Cf/HTCC-SiO2) was successfully designed and constructed through a combined hydrothermal carbonization and sol-gel process for the first time. The results revealed that the microstructure and morphology of HTCC and SiO2 coatings strongly depended on the key process parameters in the synthetic process. The optimal conditions for fabrication of Cf/HTCC-SiO2 were achieved as following: the hydrothermal temperature was 180 degrees C and holding time was 2 h; the TEOS mass fraction was 30 wt%, the distilled water/ethanol molar ratio was 6:1 and sol-gel time was 2 h, respectively. The relatively continuous and uniform HTCC/SiO2 composite coating with a single thickness about 350 and 300 nm effectively improved the mechanical and anti-oxidation of 3D needled Cf. Compared with the uncoated 3D needled Cf, the compressive strength was increased about 336% and the rapid oxidation temperature was improved about 100 degrees C after the incorporation of HTCC/SiO2 composite coating.

Automated summary

A composite coating of Cf/HTCC-SiO2 was successfully designed and constructed using hydrothermal carbonization and sol-gel processes with optimized conditions, significantly improving the mechanical and anti-oxidation properties of 3D needle carbon fibers. The resulting composite coating had a relatively continuous and uniform thickness of about 350 and 300 nm, leading to a 336% increase in compressive strength and a 100°C improvement in rapid oxidation temperature compared to uncoated fibers.